Seal assemblies for use with fluid valves

ABSTRACT

Seal assemblies for use with fluid valves are described. An apparatus includes a cage, a plug having a seal gland and a seal assembly to be at least partially positioned in the seal gland. The seal assembly includes a back-up ring having a wedge-shaped protrusion and a seal defining a wedge-shaped groove to receive the protrusion. A pressure is to act on the back-up ring to urge the protrusion into the groove. An engagement between the protrusion and the groove is to urge the seal into sealing engagement with an inner surface of the cage.

FIELD OF THE DISCLOSURE

This patent relates generally to seal assemblies and, more particularly,to seal assemblies for use with fluid valves.

BACKGROUND

Control valves are commonly used in process plants to control the flowof fluid (e.g., a gas, a liquid, etc.) or any other substance throughpipes and/or vessels to which they are connected. A control valve istypically composed of one or more inlets and outlets and includes a flowcontrol element or member (e.g., a valve gate, a piston, a valve plug, aclosure member, etc.) that operates to control fluid flow throughapertures that fluidly couple the inlet(s) to the outlet(s).

SUMMARY

One described apparatus includes a cage, a plug having a seal gland anda seal assembly to be at least partially positioned in the seal gland.The seal assembly includes a back-up ring having a wedge-shapedprotrusion and a seal defining a groove to receive the protrusion. Apressure is to act on the back-up ring to urge the protrusion into thegroove. An engagement between the protrusion and the groove is to urgethe seal into sealing engagement with an inner surface of the cage.

Another apparatus includes a cage, a plug having a seal gland and a sealassembly to be at least partially positioned in the seal gland. The sealassembly includes a male portion and a female portion to receive themale portion to urge the female portion into sealing engagement with aninner surface of the cage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a known fluid valve having a known seal assembly.

FIG. 2 depicts an enlarged view of the known seal assembly of FIG. 1.

FIG. 3 depicts an example seal assembly that can be used to implementthe examples disclosed herein.

DETAILED DESCRIPTION

Certain examples are shown in the above-identified figures and describedin detail below. In describing these examples, like or identicalreference numbers are used to identify the same or similar elements. Thefigures are not necessarily to scale and certain features and certainviews of the figures may be shown exaggerated in scale or in schematicfor clarity and/or conciseness. Additionally, several examples have beendescribed throughout this specification. Any features from any examplemay be included with, a replacement for, or otherwise combined withother features from other examples.

The examples disclosed herein relate to seal assemblies for use withvalves (e.g., flow-up valves, flow-down valves) that sealingly engage adynamic sealing surface of a cage and/or a valve plug. The sealassemblies may at least partially surround the valve plug and include ahousing, an annular portion and/or jacket defining a groove in which aflexible core is at least partially positioned. In some examples, thejacket is made of and/or includes relatively thin stainless steel (e.g.,0.004 inches) and the flexible core is made of and/or includes flexiblegraphite. While stainless steel is mentioned as an example material usedto make the jacket, any other material such as an Inconel alloy may beused.

To enable the seal (e.g., the housing, the core) to be outwardly urgedand to sealingly engage the dynamic sealing surface, the core defines awedge-shaped groove that receives a wedge and/or protrusion of a back-upring. In practice, pressure on the back-up ring urges the wedge into thewedge-shaped groove and outwardly urges and/or radially expands the sealinto sealing engagement with the dynamic sealing surface. Suchengagement between the seal and the cage and, specifically, between thehousing and the cage substantially prevents fluid from leakingtherebetween. In some examples, to reduce the frictional load on theplug and wear during throttling conditions, a biasing element and/orspring is positioned between the core and the back-up ring to urge theprotrusion away from the groove when the pressure acting on the back-upring is below a particular threshold. The biasing element and/or springmay be Belleville washers, coil springs, etc.

FIG. 1 depicts a known fluid valve 100 that has a valve body 102including a fluid flow passageway 104 between an inlet 106 and an outlet108. A bonnet 110 is coupled to the valve body 102 via a plurality offasteners 112 and includes a bore 114 to receive a stem 116. An end 118of the stem 116 extends from the bonnet 110 and is operatively coupledto an actuator, and an opposite end 120 of the stem 116 is coupled to afluid control element or plug (e.g., a pressure balanced plug) 122.

To control fluid flow through the valve body 102, valve trim 123 ispositioned between the inlet 106 and the outlet 108 to provide certainflow characteristics (e.g., to reduce noise and/or cavitation generatedby the flow of fluid through the fluid valve 100). In this example, thevalve trim 123 includes a hanging cage 124, the plug 122 and the stem116.

To prevent fluid leakage between an inner surface or dynamic sealingsurface 126 of the cage 124 and an outer surface 128 of the plug 122,the plug 122 is provided with a seal assembly 130 (shown most clearly inFIG. 2). Turning now to FIG. 2, the seal assembly 130 includes a back-upring 136, a support ring 138, a retainer 140 and a seal 132 that atleast partially surrounds a spring (e.g., a helical spring) 134.

Once the valve trim 123 is positioned in the fluid valve 100, the seal132 is urged to engage the dynamic sealing surface 126 via the spring134 to substantially prevent leakage between the surfaces 126 and 128.Additionally, when the fluid valve 100 is pressurized, the seal 132loads the back-up ring 136 such that an outer edge 142 of the back-upring 136 engages the dynamic sealing surface 126 and an inner edge 144of the back-up ring 136 engages a surface 146 of a seal gland 148 inwhich the seal 132 is at least partially positioned.

FIG. 3 depicts an example seal assembly 300 that can be used toimplement the examples disclosed herein. In this example, the sealassembly 300 includes the retainer 140, an example back-up ring and/ormale portion 302 and an example seal and/or female portion 304. In someexamples, the seal 304 includes a housing and/or annular portion 306 inwhich a core 308 and the back-up ring 302 are at least partiallypositioned. Positioning the core 308 within the housing 306 at leastpartially protects the core 308 from damage and/or erosion and enablesthe hardened wear resistant housing 306 instead of the core 308 tosealingly engage the cage 124. In some examples, the core 308 is made ofgraphite and the housing 306 is made of stainless steel.

To enable the back-up ring 302 to load the seal 304, in this example,the back-up ring 302 includes a tapered, wedge-shaped annular protrusionand/or projection 310 that is at least partially receivable within atapered and/or wedge-shaped annular groove 312 of the core 308. In someexamples, the projection 310 forms an angle of between about 15 degreesand 45 degrees. In some examples, as the back-up ring 302 moves relativeto the core 308, the back-up ring 302 slidably engages and/or is guidedby inner surfaces 314 of the housing 306.

In operation, when the fluid valve 100 is pressurized, the pressure actson a surface 316 of the back-up ring 302, which urges the back-up ring302 and the projection 310 toward the groove 312. The receipt of theprojection 310 within the groove 312 loads the seal 304 such that anouter surface and/or edge 318 of the housing 306 sealingly engages thedynamic sealing surface 126. In some examples, to reduce the frictionalload between the housing 306 and the cage 124 during throttlingconditions, a biasing element and/or spring 320 is positioned betweenthe core 308 and the back-up ring 302. The spring 320 urges theprojection 310 from the groove 312 when the pressure acting on thesurface 314 of the back-up ring 302 is below a particular threshold.

While the example seal assembly 300 is shown as being used with aflow-up valve, the seal assembly 300 may be used with flow-down valves.In such examples, the seal assembly 300 may be rotated 180 degrees fromwhat is shown in FIG. 3 and the retainer 140 may not be used. However,in some such examples, the seal assembly 300 may include a seal retainerdifferent from or similar to the seal retainer 140.

As set forth herein, an example apparatus includes a cage, a plug havinga seal gland and a seal assembly to be at least partially positioned inthe seal gland. The seal assembly includes a back-up ring having atapered protrusion and a seal defining a groove to receive theprotrusion. A pressure is to act on the back-up ring to urge theprotrusion into the groove. An engagement between the protrusion and thegroove is to urge the seal into sealing engagement with an inner surfaceof the cage. In some examples, the seal includes a core at leastpartially surrounded by an annular housing. In some examples, thehousing is stainless steel.

In some examples, the housing is U-shaped. In some examples, the back-upring is at least partially positioned within the annular housing. Insome examples, inner surfaces of the housing guide the movement of theback-up ring. In some examples, the housing is positioned between thecore and the inner surface of the cage. In some examples, the taperedprotrusion is wedge-shaped. In some examples, the core is graphite(e.g., flexible graphite). In some examples, the apparatus includes aspring positioned between the back-up ring and the core to urge theback-up ring away from the core. In some examples, the groove iswedge-shaped.

Another example apparatus includes a cage, a plug having a seal glandand a seal assembly to be at least partially positioned in the sealgland. The seal assembly includes a male portion and a female portion toreceive the male portion to urge the female portion into sealingengagement with an inner surface of the cage. In some examples, the maleportion is a wedged-shaped protrusion of a back-up ring. In someexamples, the female portion is a seal. In some examples, the sealincludes a core at least partially surrounded by a housing. In someexamples, the core includes graphite and the annular portion isstainless steel. In some examples, inner surfaces of the housing atleast partially guide the movement of the back-up ring. In someexamples, the housing is an annular housing. In some examples, theapparatus also includes a spring positioned between the core and theback-up ring to urge the back-up ring away from the core.

Another example apparatus includes a cage, a plug having a seal glandand means for sealingly engaging an inner surface of the cage at leastpartially positioned in the seal gland and including a first portion toengage and urge a second portion to sealingly engage the cage. In someexamples, the first portion is a back-up ring having a taperedprotrusion and the second portion is a seal defining a groove to receivethe protrusion.

Although certain example apparatus have been described herein, the scopeof coverage of this patent is not limited thereto. On the contrary, thispatent covers all apparatus fairly falling within the scope of theappended claims either literally or under the doctrine of equivalents.

What is claimed is:
 1. An apparatus, comprising: a cage; a plugcomprising a seal gland; and a seal assembly to be at least partiallypositioned in the seal gland, the seal assembly, comprising; a back-upring comprising a tapered protrusion; a seal defining a groove toreceive the protrusion, wherein a pressure is to act on the back-up ringto urge the protrusion into the groove, an engagement between theprotrusion and the groove is to urge the seal into sealing engagementwith an inner surface of the cage.
 2. The apparatus of claim 1, whereinthe seal comprises a core at least partially surrounded by an annularhousing.
 3. The apparatus of claim 2, wherein the housing comprisesstainless steel.
 4. The apparatus of claim 2, wherein the housing isU-shaped.
 5. The apparatus of claim 2, wherein the back-up ring is atleast partially positioned within the annular housing.
 6. The apparatusof claim 2, wherein inner surfaces of the housing guide the movement ofthe back-up ring.
 7. The apparatus of claim 2, wherein the housing ispositioned between the core and the inner surface of the cage.
 8. Theapparatus of claim 1, wherein the tapered protrusion is wedge-shaped. 9.The apparatus of claim 1, wherein the core comprises graphite.
 10. Theapparatus of claim 1, further comprising a spring positioned between theback-up ring and the core to urge the back-up ring away from the core.11. The apparatus of claim 1, wherein the groove is wedge-shaped.
 12. Aapparatus, comprising: a cage; a plug comprising a seal gland; and aseal assembly to be at least partially positioned in the seal gland, theseal assembly comprising: a male portion; and a female portion toreceive the male portion to urge the female portion into sealingengagement with an inner surface of the cage.
 13. The apparatus of claim12, wherein the male portion comprises a wedged-shaped protrusion of aback-up ring.
 14. The apparatus of claim 13, wherein the female portioncomprises a seal.
 15. The apparatus of claim 14, wherein the sealcomprises a core at least partially surrounded by a housing.
 16. Theapparatus of claim 15, wherein the core comprises graphite and theannular portion comprises stainless steel.
 17. The apparatus of claim15, wherein inner surfaces of the housing at least partially guide themovement of the back-up ring.
 18. The apparatus of claim 15, wherein thehousing comprises an annular housing.
 19. The apparatus of claim 14,further comprising a spring positioned between the core and the back-upring to urge the back-up ring away from the core.
 20. An apparatus,comprising: a cage; a plug comprising a seal gland; and means forsealingly engaging an inner surface of the cage at least partiallypositioned in the seal gland and comprising a first portion to engageand urge a second portion to sealingly engage the cage.